Electric discharge apparatus



Oct. 13,1942; R. RElTH ERMA'N :rm. 2,293,589 1 ELECTRIC DISCHARGE APPARATUS Filed Oct. 12, 1939 I INVENTORS P040}: 14 Rei zherman BY Charles M- Rowe/1 2 ATTORNEY.

Patented Oct. 13, 1942 ELECTRIC DISCHARGE APPARATUS Ralph W. Reitherinan and Charles M. Rowell, Chicago, Ill., assignors to Frank F. Rowell, Sr.,

Chicago, Ill.

Application October 12, 1939, Serial No. 299,080

3 Claims.

This invention relates to gaseous electric discharge devices of the type having thermionic cathodes, such as illuminating lamps, and more particularly to a method and means for starting and operating such devices from alternating current. As is well known, devices of this class require the application of a relatively high voltage for starting as comparedto that required for maintaining the device in operation.

Heretofore, various types'of starting and operating mechanisms and electrical circuits have been employed, practically all of which present certain objectionableconditions. In certain types of apparatus which have been used or proposed the mechanism included a time delay relay or bimetallic thermal strips in connection withwhich there usually is employed one or moresets of movable contact points which require relatively fine initial adjustment for proper functioning of the apparatus, and which contacts, in a short period of time, deteriorate by constant arcing, resulting in inefiicient and slow starting of the lamp. Also, in certain types of apparatus of this class, the cathodes are only heated for efiecting electronic emission across the cathodes to initially start the lamp. It has been foundth J in such apparatus, small particles of the cathodes are constantly being broken off the main body, reducing the life of the. cathodes. Furthermore, such deterioration of the cathodes results in more difficult starting; reduced life of the lamp; blackening of the ends of the lamp; reduced efliciency of the lamp; and detracts from its appearance.

One of the objects of this invention is to provide improved apparatus of the above mentioned character which maintains the cathodes heated during both starting and operation of the lamp and which eliminates all of the above mentioned objectional characteristics of apparatus hereto fore employed.

Another object is to provide simple and improved apparatus of the character indicated, including a balanced circuit and novel means for limiting the cathode heating current after the lamp is operating.

A further object is to provide improved apparatus of the character indicated, which is durable, highly efficient, effects quick starting of lamp, and capable of being economically manufactured.

Other objects and advantages of the invention will be apparent from the following description, taken in connection with the accompanying drawing, in which-- "of volts.

Fig. I is a diagrammatic illustration of an electrical circuit embodying one form of the present invention.

Fig. 2 is a diagrammatic illustration of an electrical circuit embodying another form of this invention, in which circuit a capacitor is connected in shunt across the cathodes of the electric discharge lamp. 1 5.1

Fig. 3 is a diagrammatic illustration oi anelectrical circuit embodying a further modification of our invention, wherein the inductance; and transformer are magnetically coupled. v

In the diagrammatic electrical circuit illustrated in Fig. l, the gaseous electric discharge device comprises a lamp ID, of the'commerclally known fluorescent type including an interiorlycoated, elongated, sealed, glass tube containing a suitable gaseous filling, such as argon or neon together with particles of mercury, and having thermionic cathodes II and I2, of the electron emissive type, disposed adjacent opposite ends thereof. One terminal of cathode l l is connected to a conductor wire 14, the free end of which is connected to a main source of alternating current of usual line voltage, such as in the range A corresponding terminalof cathode IZ is connected by a conductor wire IE to a ballast inductance or swinging choke coil IS, the opposite end of which coil is connected by a. conductor wire I! to the main source of current. It is to be understood that a suitable switch (not shown) may desirably be connected in either of conductor wires 14 or H. The circuit thus far described, in which the lamp l0 and inductance l6 are in series, constitutes the normal operating circuit for the lamp. Obviously, however, this circuit is not self-starting for two reasons; namely, first, some means must be provided for preheating the cathodes H and I2 to obtain electronic emission, and second, the negative static charge on the glass wall of the lamp must be overcome.

In the electrical circuit illustrated, the cathodes are heated constantly during the entire period the lamp III is operating. The heating of the cathodes is accomplished by means of a trans former l8, including a primary coll secondary coils 20 and 2|. One end of the primary coil IQ of the transformer is connected in series with the secondary coil 20 to the main conductor wire l4, and a conductor wire 22 connects the other terminal of cathode II to the junction of said primary coil 19 and secondary coil 20. The other end of the primary coil is connected by a conductor wire 23 to a tap 2|,

taken out on the ballast inductance or choke coil I 6. The secondary coil 2i is connected at one end to the conductor wire l5, and at the other end by a conductor wire 25 to the other terminal of .cathode l2.

volts per turn ratio must be substantially lower in transformer l8 than in inductance or choke 0011 ii, and the core cross-section of said transformer must be substantially greater than the core cross-section of said inductance or choke coil. [6, provided that steel of the same permeability be used in both cores. This will cause a drop in potential across the respective windings involved proportional to the differential in volts g per turn ratio between primary l9 and inductance or choke coil l6. This relationship makes it possible to obtain a rise in voltage output from said choke coil IB'for that portion of the operating cycle that choke coil I6 i in the circuit as an auto-transformer, which is at the time the cathodes II and I 2 are being heated preparatory to striking of the arc across the cathodes. It

has been found that the momentary potential rl'se necessary for dissipating the static charge on the wall of the lamp ID, with a lamp within the range of 15 Or watt capacity and a normal input of 115 volts, is between 700 and 800 volts, depending upon the humidity and other atmospheric conditions. Toaccomplish such increase in potential, the turn ratio of that portion of the inductance coil l6 between the tap 24 and wire H to the remainder of said coil I6 is approximately '7 to 1 in the inductance or choke coil 16, with a normal input of 115 volts.

When the circuit is closed for energizing the lamp ID, the transformer I8 immediately functions to cause heating of the cathodes H and I! for causing electronic emission, and substantially simultaneously the high potential produced by the inductance coil l6, operating as an autotransformer, is impressed across the cathodes H and i2. This high'potential breaks down and dissipates the static charge on the wall of the lamp and permits establishment of an are from one cathode to the other. The are current thus flowing causes the iron cor of the inductance coil to become saturated, and causes the imped-- ance to rise across that portion of the inductance coil l6, between the tap 24 and the connection to conductor i1, and thereby functions to limit the cathode heating current produced by transformer [8 in inverse proportion to the leakage react'ance' of .the inductance coil IS. The lamp Ill thereafter functions in a circuit including the lamp and inductance coil in series, at a relatively.

reduced voltage, and th cathodes are maintained heated by the limited current flowing through the transformer l8.

Due to the swinging characteristics of th inductance or choke coil I6, any desired amount of cathode current maybe caused to flow continuously under normal operation, so that the deterioration of the cathodes is controlled and may be substantially reduced. By correcting the deterioration of the cathodes, which takes place in connection with practically all present type apparatus of this class due to the fact that in these circuits the cathodes are in reality operated as self-energized cathodes with the accompanying high cathode drop, which has a tendency to limit the life of the cathode thus energized, the life of the lamp is substantially increased, and the blackening of the ends of the lamp tube in operation eliminated so as to maintain high efliciency of the lamp, good appearance, and ease of starting of the lamp.

The circuit illustrated in Fig. 2, in the main, is, with one exception, identical with the circuit shown in Fig. 1, as above described, and for convenience, corresponding parts ar accorded the same numerical designation together with the exponent a." The exception referred to comprises the addition of a capacitor 26, connected by conductor wires 21 and 28*, to the upper terminal of cathodes II and I! in shunt relation. The purpose of the capacitor is to draw of! the high static charge on the wall of the tube of the lamp 10 to facilitate starting of th lamp. The circuit represented in Fig. 2 otherwise functions exactly as the circuit of Fig. 1, as above described.

The modified electrical circuit diagrammatically illustrated in Fig. 3 is, with one main exception, the same as the circuit shown in Fig. 1, and for convenience, corresponding parts are accorded the same numerical designation together with the exponent b. The difference between the circuits shown in Figs. 1 and 3 consists in the provision of the ballast inductance coil I!" in .magnetically coupled relation to the transformer l8". This relationship permits using additional magnetic flux of said transformer with the ballast inductance for expeditiously building up the high potential necessary for establishment of the arc between the cathodes. By virtue of such relationship between the inductance and transformer, it is possible to attain a higher voltage for causing arcing between cathodes without the usual loss attendant upon use of coils whose magnetic fields are separated.

Although there is herein shown certain preferred embodiments of the invention, manifestly it is capable of modification and rearrangement without departing from the spirit and scope thereof. It is not, therefore, intended that the present invention be limited to the precise forms herein shown and described, except as it may be so limited in the appended claims.

We claim:

1. Starting and operating apparatus for a gaseous electric discharge devicehaving thermionic cathodes, said apparatus comprising conductor wires connecting one terminal of each of saidcathodes in series with a source ofalternating current, a ballast inductance interposed in one of said conductor wires in series with said cathodes, and a transformer including a primary and two secondaries, each of said secondaries being connected to the terminals of one of the respective cathodes, and said primary being connected at one end to said ballast inductance and the other end being in. series with the secondary connecting the cathode, one terminal of which is connected to the other conductor wire, said inductance and transformer being magnetically coupled, and the core cross-section of said transformer being substantially greater than the core cross-section of said inductance, whereby the voltage is initially increased to cause electro ic aacJssc flow between the cathodes and whereupon said inductance serves to ballast the circuit to main tain electronic flow at reduced voltage.

2. Starting and operating apparatus fir a gaseous electric discharge device having thermionic cathodes; said apparatus comprising conductor wires connecting one terminal of each of said cathodes in series with a source of alternating current, a ballast inductance interposed in one of said conductor wires in series with said cathodes, and a transformer including a primary and two secondaries, each of said secondaries being connected to the terminals of one of the respective cathodes, and said primary being connected at one end to said ballast inductance at a point intermediate its length and the other end of said primary being in series with the secondary connecting the cathode, one terminal of which isconnected to the other conductor wire, said inductance and transformer being magnetically coupled and the core cross-section of said transiormer being substantially greater than the core cross-section 01' said inductance, whereby the voltage is initially increased to cause electronic flow between'the cathodes and whereupon said inductance serves to ballast the circuit to maintain electronic flow at reduced voltage, and whereby the portion of the ballast inductance in circuit with said primary, after electronic flow in one of said conductor wires in series with said cathodes, and atransformer including a primary and two secondaries, each of said secondaries being connected to the terminals of one of the respective cathodes, and said primary being connected at one end to a tap taken out on said swinging ballast inductance at a point intermediate its length, and the other end being in series with the secondary connecting the cathode, one

terminal of which is connected to the other conductor wire, said inductance and transformer being magnetically coupled and the core cross-section of said transformer being substantially greater than the core cross-section of said inductancej whereby the voltage is initially increased to cause electronic 'flow between the cathodes and whereupon said inductance serves to ballast the circuit to maintain electronic flow at reduced voltage.

RALPH W. REITHERMAN. CHARLES M. ROWELL. 

